Click events in android

Android Input Events (Event Listeners, Event Handling)

In android, Input Events are used to capture the events, such as button clicks, edittext touch, etc. from the View objects that defined in a user interface of our application, when the user interacts with it.

To handle input events in android, the views must have in place an event listener. The View class, from which all UI components are derived contains a wide range event listener interfaces and each listener interface contains an abstract declaration for a callback method. To respond to an event of a particular type, the view must register an appropriate event listener and implement the corresponding callback method.

For example, if a button is to respond to a click event it must register to View.onClickListener event listener and implement the corresponding onClick() callback method. In application when a button click event is detected, the Android framework will call the onClick() method of that particular view.

Generally, to handle input events we use Event Listeners and Event Handling in android applications to listen for user interactions and to extend a View class, in order to build a custom component.

Android Event Listeners

In android, Event Listener is an interface in the View class that contains a single call-back method. These methods will be called by the Android framework when the View which is registered with the listener is triggered by user interaction with the item in UI.

The following are the call-back methods included in the event listener interface.

Method	Description
onClick()	This method is called when the user touches or focuses on the item using navigation-keys or trackball or presses on the «enter» key or presses down on the trackball.
onLongClick()	This method is called when the user touches and holds the item or focuses on the item using navigation-keys or trackball and presses and holds «enter» key or presses and holds down on the trackball (for one second).
onFocusChange()	This method is called when the user navigates onto or away from the item, using the navigation-keys or trackball.
onKey()	This method is called when the user is focused on the item and presses or releases a hardware key on the device.
onTouch()	This method is called when the user performs a touch event, including a press, a release, or any movement gesture on the screen.
onCreateContextMenu()	This method is called when a Context Menu is being built.

There are many more event listeners available as a part of View class to use it in our android applications.

Android Event Listeners Registration

In android, Event Registration is the process by which an Event Handler gets registered with an Event Listener so that the handler is called when the Event Listener fires the event.

Following are the different ways to register event listeners in our android applications.

• By specifying event handlers directly in activity_main.xml file, we can register event listeners
• By using Activity class that implements a listener interface, we can register event listeners
• By using an anonymous class.

Following is the example of registering a Button onClick event listener in android application.

@Override
protected void onCreate(Bundle savedInstanceState) <
….
// Capture button from our layout
Button button = (Button)findViewById(R.id.btnShow);
// Register onClick listener with the below implementation
button.setOnClickListener( btnListener );

….
>
// Anonymous implementation of OnClickListener
private View.OnClickListener btnListener = new View.OnClickListener() <
public void onClick(View v) <
// do something when the button is clicked
>
>;

This is how we can register our event listeners in different ways based on our requirements.

Android Event Handlers

In android, Event Handlers are useful to define several callback methods when we are building custom components from view.

Following are the some of commonly used callback methods for event handling in android applications.

Method	Description
onKeyDown()	This method is called when a new key event occurs.
onKeyUp()	This method is called when a key up event occurs.
onTrackballEvent()	This method is called when a trackball motion event occurs.
onTouchEvent()	This method is called when a touch screen motion event occurs.
onFocusChanged()	This method is called when the view gains or loses focus.

Now we will see how to define input Events using Even Listeners and Event Handling with examples in android applications.

Android Input Events Example

Following is the example of defining an input controls Button, TextView in user interface and showing the text in TextView when users click on Button in the android application.

Create a new android application using android studio and give names as InputEventsExample. In case if you are not aware of creating an app in android studio check this article Android Hello World App.

Now open an activity_main.xml file from \res\layout path and write the code like as shown below

activity_main.xml

If you observe above code we created a one Button and TextView control in XML Layout file to show the text in textview when we click on Button.

Once we are done with the creation of layout with required controls, we need to load the XML layout resource from our activity onCreate() callback method, for that open main activity file MainActivity.java from \java\com.tutlane.inputeventsexample path and write the code like as shown below.

MainActivity.java

package com.tutlane.inputeventsexample;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;

public class MainActivity extends AppCompatActivity <
Button btn ;
TextView tView ;
@Override
protected void onCreate(Bundle savedInstanceState) <
super .onCreate(savedInstanceState);
setContentView(R.layout. activity_main );
btn = (Button)findViewById(R.id. btnClick );
tView = (TextView)findViewById(R.id. txtResult );
btn .setOnClickListener( new View.OnClickListener() <
@Override
public void onClick(View v) <
tView .setText( «You Clicked On Button» );
>
>);
>
>

If you observe above code we registered our Button click event using setOnClickListener event listener and binding a data to TextView control when we click on button.

Generally, during the launch of our activity, onCreate() callback method will be called by android framework to get the required layout for an activity.

Output of Android Input Events Example

When we run above example using android virtual device (AVD) we will get a result like as shown below

If you observe above result, we are getting binding a text to textview control on button click. This is how we can handle input events in android applications based on our requirements.

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Button Click Me setOnClickListener Method Working — Java Android

Button will respond to OnClickListener after this course.

This example demonstrates the implement button onclicklistener android java Code Example

In this article, we will discuss about how to trigger click events on android Views (Buttons, Text views etc) ?

Android Button in JAVA ANDROID

Action listeners are probably the easiest — and most common — event handlers to implement. You implement an action listener to define what should be done when an user performs certain operation.

Step 1 − Create a new project in Android Studio, go to File ⇒ New Project and fill all required details to create a new project.

Create Empty Project

How to implement on Android Button OnClick in android programmatically.

S tep 2 — “Add the following code to res/layout/activity_main.xml.“

I worked in simple relative layout method for only give basic example.

• In the below code, we have declared Button as ”@+id/button”.
• You can add a spinner to your layout with the Button object. You should usually do so in your XML layout with a element. For example:

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Input Events in Android with Example

In Android, there’s quite a method to intercept the events from a user’s interaction with your application. When considering events within your interface, the approach is to capture the events from the precise View object that the user interacts with. The View class provides the means to try to do so. Within the varied View classes that you’re going to use to compose your layout, you’ll notice several public callback methods that look useful for UI events. These methods are called by the Android framework when the respective action occurs thereon object. For instance, when a View (such as a Button) is touched, the onTouchEvent() method is named thereon object. However, to intercept this, you must extend the class and override the method. However, extending every View object to handle such an event would not be practical. This is why the View class also contains a set of nested interfaces with callbacks that you simply can far more easily define. These interfaces, called Event listeners, are your ticket to capturing the user interaction together with your UI.

For Example, if a button is to reply to a click event it must register to look at the .onClickListener event listener and implement the corresponding onClick() callback method. In an application when a button click event is detected, the Android framework will call the onClick() method of that particular view.

Android Event Listeners

Event Listener is an interface within the View class that contains one call-back method. These methods are going to be called by the Android framework when the View which is registered with the listener is triggered by user interaction with the item in UI. Included in the event listener interfaces are the following callback methods:

Description

onClick()

This method is called when the user touches the item or focuses upon the item with the navigation-keys or trackball and presses the suitable “enter” key or presses down on the trackball.

onLongClick()

This is called when the user either touches and holds the item, or focuses upon the item with the navigation-keys or trackball and presses and holds the suitable “enter” key or presses and holds down on the trackball (for one second).

onFocusChange()

This is called when the user navigates onto or away from the item, using the navigation-keys or trackball.

onKey()

This is called when the user is focused on the item and presses or releases a hardware key on the device.

onTouch()

This is called when the user acts qualified as a touch event, including a press, a release, or any movement gesture on the screen (within the bounds of the item).

onCreateContextMenu()

This is called when a Context Menu is being built (as the result of a sustained “long click”).

onClick() callback does not return any value. But onLongClick(), onKey(), onTouch() callback returns a boolean value that indicates that you simply have consumed the event and it should not be carried further; That is, return true to indicate that you have handled the event and it should stop here; return false if you’ve not handled it and/or the event should continue to any other on-click listeners.

Android Event Listener Registration

Event Registration is the process by which an Event Handler gets registered with an Event Listener so that the handler is called when the Event Listener fires the event. This example illustrates how to register an on-click listener for a Button

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Technology Talks

on Microsoft technologies, Web, Android and others

Android : Using Button & Click-Event with example

Introduction :

In this article we will learn, how to use Button and Listen for Click-Events. We shall take an example to understand all these . To make the example clear and easy to understand we shall use another control called EditText.

Implementation using Example :

• Create a new android project with name ButtonTutorial.
  [If you are a beginner and don’t know how to create a project then read it here Creating HelloWorld Application in Android]
• Type you application name as My Button Tutorial.
• Provide package name as com.suvendu.tutorials.button
• Open main.xml and delete the single TextView already present in the page(may be with a text ‘Hello World, ButtonTutorialActivity!’.
• Drag a EditText and a Button on to the layout.
• Change the id of the EditText to ‘@+id/txtShowCurTime‘
• Change the id of the Button to ‘@+id/btnGenCurTime‘
• Add a new string to strings.xml with Name‘button’ and Value ‘Generate Current Time‘
• Change the text of the Button to ‘@string/button’
  [Your layout is ready now and the main.xml should look like this]
  

Open your default activity file (Ex: ButtonTutorialActivity.java)

Declare two global variables

import respective packages

Link these variables to the layout in OnCreate() as follows

We don’t want the OnScreenKeyBoard to appear when the cursor is on EditText so, let disable this.

import the package for OnClickListener

Now do the logic inside onClick() to show the current time

You need to import java package for using Date

Finally, the default activity file should look like

Downloads :

You can download the full project here.

Or, you can just download the apk here.

Conclusion :

We are able to use a Button control in Android and can use its OnClick event to do various activities.
I hope you enjoyed this tutorial.

Please give your valuable feedback and stay tuned for more ..

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